Abstract 3523: C7, C9-dimethylifosfamide analogs evaluation for antitumor activity and toxicity: Detoxification pathways might explain nephrotoxicity

Abstract

Abstract Ifosfamide (IFO) is an anticancer drug, widely used against various types of human solid tumors. This prodrug produced active alkylating isophosphoramide mustard. But its side-chain oxidative metabolism is associated with toxicities in high-dose chemotherapy. As acrolein urotoxicity is limited by coadministration of mesna, chloroacetaldehyde (CAA) is responsible for neurotoxicity and nephrotoxicity. C7, C9 dimethyl-ifosfamide analogs have been synthesized to prevent these side effects. In vitro metabolism and anticancer activity investigations demonstrated that the generated dimethylated mustards were faster alkylating agents (28 fold faster) than isophosphoramide mustard and IC50 values on 9L glioblastoma cells showed higher cytotoxicity of analogs, especially the 7S,9S enantiomer (1). This later was selected for in vivo investigations. As these analogs were still metabolized through the same N-deschloroalkylation pathway, monoochloroacetone (MCA) is produced instead of CAA. In a first step, in vitro/ex vivo experiments were conducted to investigate its toxicity. The toxicity of both metabolites was compared by evaluation of cell viability using canine kidney cell lines (MDCK) and rabbit renal proximal tubules (RRPT). Cell viability experiments showed that similar IC50 values were obtained for CAA and MCA (21 and 23 µM) on MDCK. To determine detoxification pathways, several experiments were conducted on RRPT. Whereas these compounds could react directly with glutathione (GSH), identification of GSH and its conjugates (GSR) was performed by LC/MS after incubation of MDCK and RRPT with 200 µM CAA and MCA. Both enzymatic reduction and GSH conjugation pathways occurred. Conjugates were then quantified by LC-MS/MS over 1-650 µM for GSH and over 1-200 µM for GSR from 20 to 120 min. The results demonstrated a rapid depletion of GSH and few differences in detoxification's kinetics for CAA and MCA. As MCA in vivo generated levels are still unknown, 7S,9S dimethyl-IFO analog is currently under investigation on human tumor cells xenografted in mice in order to confirm its antitumor activity and to evaluate its toxicity. (1) Storme T, Deroussent A, Mercier L, Prost E, Re M, Munier F, Martens T, Bourget P, Vassal G, Royer J and Paci A. J Pharmacol Exp Ther. 2009, 328(2):598-609. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3523.